INTRODUCTORY OBSERVATIONS. 



SYNOPSIS OF PRIMARY DIVISIONS OF THE POLYZOA. 



I. Lophophore bilateral, mouth with an epistome. 



Order I. PHYLACTOLuEMATA, Allm. 



(a) Arms of lophophore, free or obsolete. Consistence horny, subcalcareous. 

 Sub-Order I. LOPIIOPEA (freshwater). 



(4) Arms of lophophore united at the extremities. Consistence soft, fleshy. 

 Sub-Order II. PEDICELLINEA (marine). 



II. Lophophore orbicular, or nearly so ; no epistome. 



Order II. GYMNOL^IMATA, Allm. 



(it) Polypide completely retractile ; evagination of tentacular sheath imperfect. Consistence 

 horny or subcalcareous. 



Sub-Order III. PALUDICELLEA (fresh-water). 



(4) Polypide completely retractile; evagination perfect; orifice of cell sub-terminal, of less 

 diameter than the cell, and usually closed with a moveable lip or shutter; sometimes by a 

 contractile sphincter ; cells not tubular. Consistence calcareous, corneous, or fleshy. 



Sub-Order IV. CHEILOSTOMATA, Busk (marine). 



(4) Cell tubular ; orifice terminal, of same diameter as the cell, without any moveable apparatus 

 for its closure. Consistence calcareous. 



Sub-Order V. CYCLOSTOMATA, Busk (marine). 



(c) Orifice of cell terminal, furnished with a usually setose fringe for its closure ; cells distinct, 

 arising from a common tube. Consistence horny or carnose. 



Sub-Order VI. CTENOSTOMATA, Busk (marine). 



Of these Orders and Sub-orders, we may at once, in a palseontological point of view, 

 dismiss from consideration all but the Cheilostomaia and Cyclostomata, to which alone, 

 so far as is at present certainly known, do any fossil remains belong. The reason of this 

 has already been explained, or will be obvious upon a glance at the characters of the 

 orders in the foregoing synopsis. 



